1. Field of the Invention
Disclosed embodiments of the invention generally relate to pressure vessels for high pressure treatment processes, and more particularly, to temperature sensors and associated connectors positioned within such vessels.
2. Description of the Related Art
Pressure vessels are commonly used in various industries for manufacturing and product treatment. Typically, a pressure vessel includes a cylindrical body and upper and lower closures, which are used to close the ends of the cylindrical body. The product or device to be treated is placed within the pressure vessel, the vessel is filled with a pressure medium, and the interior of the vessel is subjected to extremely high pressures, generally ranging between about 40,000 psi and 100,000 psi. Such vessels must therefore be extremely robust to withstand such pressures.
Increasingly, pressure vessels of the type described above are employed for the treatment of products such as food, medical, and biological products. Liquid products, such as beverages, are especially amenable to treatment in pressure vessels, though a wide range of other types of products are also treatable. When a product is placed within a pressure vessel and subjected to such extreme pressures, all living organisms within or on the product are destroyed, effectively sterilizing the product.
The products to be treated are placed in non-rigid containers which are then positioned within the vessel. Remaining space in the vessel is filled by a pressure medium, usually water. The vessel is sealed and subjected to ultra-high pressures, which isostatically press the containers of product. Because of the non-rigid nature of the containers, the containers are able to tolerate the distortion caused by the pressure, due, mostly, to the presence and compression of trapped gasses, such as air bubbles, in the containers.
Frequently, product treatment includes both pressure treatment and temperature treatment. In such cases, it is common to exploit well known adiabatic principles to perform at least a portion of the heat treatment of the product within the pressure vessel. It is well known that temperature, pressure, and volume of a given substance are interrelated. Where the volume is held constant, a rise in pressure will result in a corresponding rise in temperature. If the adiabatic characteristics of a given material are known, a change in temperature can be calculated for a given change in pressure. Thus, in principle it is possible to subject a known product surrounded by a known pressure medium to a selected degree of pressure and predict the temperature that will be reached within the vessel during the pressing process.
However, in practice, several problems may arise. Because different substances have different adiabatic properties, a variety of products placed together within a pressure vessel for pressure treatment can produce thermal gradients within the vessel. Additionally, the vessel, itself, can act as a heat sink, drawing heat from within the vessel. Placement of the product within the vessel and the thermal conduction characteristics of the vessel can affect thermal distribution within the vessel. Under such circumstances, it can be difficult to predict the exact temperature within the vessel, and whether the temperature is consistent throughout. Finally, health codes and regulations that relate to the treatment of food products require that actual temperature measurements be taken during the processing of the food products, to ensure that the product is safely processed. For all of these reasons, it is desirable to have temperature sensors within a pressure vessel while a food product is being treated.